1. Field of the invention
The present invention relates to a device for the formation, by pyrolysis, of a coating of metal or metal compound on one face of a moving hot glass substrate by bringing said face into contact with a gaseous reagent, comprising support means for conveying the substrate through a coating chamber, at least one reagent gas inlet for supplying and distributing reagent gas to the coating chamber and at least one exhaust gas outlet for discharging exhaust gas from the coating chamber, and also to a method for forming a coating of metal or metal compound on a moving hot glass substrate by pyrolysis of a reagent in the gaseous phase.
The coating of metal or metal compound formed on a hot glass substrate by pyrolysis is used for modifying the apparent colour of the glass and/or presenting other properties required vis-a-vis incident radiation, for example the property of reflecting infrared. A single coating on the glass substrate may be used for these purposes, or a multi-layer coating. Examples would be coatings of tin oxide SnO.sub.2, tin oxide SnO.sub.2 doped with fluorine, titanium dioxide TiO.sub.2, titanium nitride TiN, silicon nitride Si.sub.3 N.sub.4, silica SiO.sub.2 or SiO.sub.x, alumina Al.sub.2 O.sub.3, vanadium pentoxide V.sub.2 O.sub.5 or tungsten oxide WO.sub.3 or molybdenum oxide MoO.sub.3, and in general oxides, sulfides, nitrides or carbides and a layering of two or more of these coatings.
The coating can be formed on a sheet of glass which moves in a tunnel oven or on a glass ribbon during formation, whilst it is still hot. The coating can be formed inside the lehr which follows the glass ribbon forming device or inside the float tank on the top face of the glass ribbon whilst the latter is floating on a bath of molten tin.
2. Description of the Related Art
To form the coating, the substrate is brought into contact, in a coating chamber, with a gaseous medium comprising one or more substances in the gaseous phase. The coating chamber is fed with a reagent gas through one or more slots, the length of which is at least equal to the width to be coated, fed through one or more ejection nozzles. Depending on the type of coating to be formed and the reactivity of the substances used, if several substances have to be used, these are distributed either in the form of a mixture by a single ejection nozzle in the coating chamber via a slot, or separately by several ejection nozzles via separate slots.
Methods and devices for forming such a coating are described for example in French patent No 2 348 166 (BFG Glassgroup) or in French patent application No 2 648 453 A1 (Glaverbel). These methods and devices lead to the formation of particularly strong coatings with advantageous optical properties.
While such devices may be capable of forming coatings of acceptable quality, it is a disadvantage of such devices that some coating material is spuriously deposited on other surfaces adjacent the coating chamber, in particular on the roof thereof and that over time such deposits may build up and disturb the flow of reagent gas through the coating chamber thereby resulting in uneven coating or may even fall onto the glass surface thereby resulting in even more serious defects.